1. Field of the Invention
The present invention relates to a method of forming charged particle beam pattern writing data. For example, the present invention relates to a method of forming charged particle beam pattern writing data which forms pattern writing data from layout data of a circuit serving as design data. The pattern writing data is data to write a predetermined pattern while deflecting a charged particle beam.
2. Related Art
A lithography technique which leads development of micropatterning of a semiconductor device is a very important process which uniquely generates a pattern in semiconductor manufacturing processes. In recent years, with high integration of an LSI, a circuit line width required for semiconductor devices progressively decreases year after year. In order to form a desired circuit pattern on the semiconductor devices, a high-definition original pattern (also called a reticle or a mask) is necessary. In this case, an electron beam writing technique has an essentially excellent resolution and is used in production of a high-definition original pattern.
FIG. 31 is a conceptual diagram for explaining an operation of a conventional variable-shaped electron beam photolithography apparatus. A variable-shaped electron beam photolithography apparatus (EB (Electron Beam) writing apparatus) operates as follows. In a first aperture 410, a square, for example, rectangular opening 411 to shape an electron beam 442 is formed. In a second aperture 420, a variable-shaped opening 421 to shape the electron beam 442 having passed through the opening 411 in a desired square shape is formed. The electron beam 442 irradiated from a charged particle source 430 and having passed through the opening 411 is deflected by a deflector. The electron beam 442 passes through a part of the variable-shaped opening 421 and is irradiated on a target object 440 placed on a stage. The stage continuously moves in one predetermined direction (for example, defined as an X direction). More specifically, a square shape which can pass through both the opening 411 and the variable-shaped opening 421 is written in a writing region of the target object 440. A scheme which causes an electron beam to pass through both the opening 411 and the variable-shaped opening 421 to form an arbitrary shape is called a variable shaped beam scheme.
When the electron beam writing is to be performed, first, a layout of a semiconductor integrated circuit is designed. Layout data (design data) is then generated. The layout data is converted to generate pattern writing data for use in an electron beam writing apparatus. On the basis of the pattern writing data, a figure is split into shot sizes to actually shoot an electron beam to perform writing.
A pattern writing region of a target object is virtually split into a plurality of strip-like frame regions each having a deflectable width of a deflector along, for example, a Y direction. Writing is performed on the split frame regions while moving a stage having the target sample placed thereon and causing a single-stage or multi-stage deflector to deflect an electron beam. Upon completion of the writing on the first frame region, the stage moves in the Y direction. Next writing on the second frame region is performed. In this case, writing on the second frame region while moving the stage in an X direction. In this manner, writing is sequentially performed on the respective frame regions.
In this case, with respect to a method for electron beam writing in which a stage moves by a step-and repeat scheme when the stage moves in the X direction within one frame, the following technique is disclosed. More specifically, a pattern is split to eliminate a deviation of a pattern ranging over regions subjected to writing before and after mechanical movement. The technique decreases a dose depending on the number of split patterns (for example, see Published Unexamined Japanese Patent Publication No. 04-176114 (JP-A-04-176114)). A case in which there is a pattern ranging over sub-fields obtained by further splitting a main deflection region having a frame width angle is disclosed as the following technique. More specifically, a boundary position of the sub-fields is changed with reference to the pattern ranging over the sub-fields to prevent the pattern from ranging over the sub-fields (for example, see Published Unexamined Japanese Patent Publication No. 11-67648 (JP-A-11-67648)).
The pattern writing apparatus includes a single-stage or multi-stage deflection region. With respect to an area running out of a deflection region, deflection of a charged particle beam by a deflector does not reach the deflection region to make it impossible to writing. For this reason, when a pattern (for example, cell) ranging over deflection regions is desired to be arranged, the following countermeasure must be taken in formation of layout data. More specifically, a cell must be split in advance so as to prevent the cell from running out of the deflection region, to thereby form layout data. In this case, one cell is defined in a plurality of deflection regions. For this reason, pieces of information and the like of an arrangement position and a size of the cell are necessary. As a result, an amount of the layout data disadvantageously increases.
When there are cells which can be essentially obtained to have an array structure, the following countermeasure must be taken if some or all elements of the cells ranging to another deflection region. More specifically, the cells are purposely developed into arrays and must be defined in deflection regions which are arranged for the respective cells. Accordingly, pieces of information related to the cells are required. As a result, an amount of layout data disadvantageously increases.
As described above, when an amount of the layout data, especially, on the upstream side increases in a data conversion process, time required to convert data increases in the case of converting the layout data into pattern writing data. Furthermore, in addition to this, huge amounts of time are disadvantageously required to transmit the data to a conversion apparatus. In an increase in amount of data with an increase in integration density of LSIs in recent years, the increase in amount of data on the upstream side also influences a throughput of a pattern writing apparatus. When the amount of data is small, time (for example, format check) required to determine correctness of layout data can be reduced.